There’s just enough of the old stone foundation for the mind’s eye to imagine the Ye Alpine Tavern in its glory days. Here, in a grove of oaks and spruces, stood a quaint stone inn with rocking chairs on a wide veranda and parlor dancing in the cool mountain air.It was Disneyland in its day, a resort at the end of the Mt. Lowe Railway, a tortuous, winding, three-mile train line up the mountain that was considered one of the world’s engineering marvels. Three million people came to visit the spot before it burned to the ground in 1936.

Today, the site is a campground and a resting place for hikers and trail runners who follow the Sam Merrill Trail and then the old rail bed up from Altadena, a five-mile journey.

If this was an indispensable trip for tourists to Southern California at the turn of the century, the same might be said today for any visitor intrigued by the San Gabriel Mountains — so close to Los Angeles and yet so seemingly impenetrable.And hiking up the Sam Merrill Trail to the old Mt. Lowe railroad bed is the perfect introduction to the mountain trail experience. For starters, the Sam Merrill is a single-track trail, not a fire road, meaning it is only wide enough in most places for one.

The Sam Merrill may be the most accessible trail in all of Angeles National Forest. It begins where Lake Avenue in Altadena, ends — with ample parking on the street. The trail is smooth and well-defined but rocky enough underfoot at times to make hiking boots sensible, especially where rock slides partially obscure the path. The slides were numerous during the heavy winter rains, but hikers quickly beat new paths through the rock and dirt.

The grade is challenging but “very runnable,” says Andy Kumeda, 37, director of information technology for the National Childhood Cancer Foundation. He’s running to Echo Mountain, a 1,400-foot gain where the lower portion of the Sam Merrill Trail ends and the railroad bed continues up to the top of Mt. Lowe.

Not too far behind him are Roy and Karen Marquedant. They’re dressed in windbreakers because, serious hikers, they know how much colder it can be at the summit. Roy, retired from NASA’s Jet Propulsion Laboratory, has a hiking pole in one hand.

The switchbacks they’re traversing leave no doubt that the Sam Merrill is carved into a mountain, and the sheer cliff off one side of the trail leaves little room for error. This isn’t a dangerous trail, but it’s not to be taken for granted either.

About three miles up, interpretive signs make it possible to visualize most of the old rail bridges, whose abutments still dot the mountainside. One of the signs bears a picture of the ninth bridge that was required to get the train up to the Cape of Good Hope.

Another shows a rail car entering “Granite Gate,” a rock outcropping that’s survived the railroad by almost 70 years. And of course there’s the location of the tavern.

On weekends, the Sam Merrill Trail is crowded by Angeles National Forest standards.

A hike to the top and back means encountering a dozen other people. But farther up, even on weekends, the numbers drop precipitously and hiking the trail becomes a solitary experience. The Ye Alpine Tavern site, once Southern California’s most famous tourist attraction, is often deserted.

On weekday mornings, the numbers thin and the trail belongs to regulars, such as Kumeda and the Marquedants, and Joel Lefkowitz, 55, a registered nurse who works for Kaiser Permanente.

“You get the experience of being in the mountains,” Lefkowitz says, out with his dog, Fawny. “I’m late this morning. Normally I start between 6 and 6:30. I see the same people. We kind of know each other — a lot of dog people.”

It’s hard to tell who feels more liberated, him or his dog. “For a dog to be off leash — it’s so good,” says Lefkowitz, wearing a morning beard, a sweatshirt and hiking shorts. “It’s how their nature is, they can sniff and look at things. They’re more of a companion.”

“It’s just incredible, in an area of how many millions of people,” he says, “there’s just a handful up there.”

The particulars

Where: Sam Merrill Trail to the Mt. Lowe Trail Camp above Altadena.

What: A moderate 10-mile hike that starts at the top of Lake Avenue, ascends through a number of switchbacks to Echo Mountain and continues along the Mt. Lowe railroad bed, where interpretive signs lead you to the site of the tavern. Elevation loss and gain is 2,600 feet.

How: Exit the 210 Freeway at Lake Avenue, drive north to the top of Lake Avenue where it ends. Parking is on the street.